Dryer construction



5 Sheets-Sheet 1 Filed Sept. 1.7. 1962 July 5, 1966 R. c. voNDERAU 3,258,851

DRYER CONSTRUCTION Filed Sept. 1.7, 1962 5 Sheets-Sheet 2 /J w n w m A 5 A 7 A x2 d 6 INVENTOR. Ra/vzod'l/zderdd BY I W/ @40 96 A A ORNE YS July 5, 1966 R. c. voNDERAU 3,258,851

DRYER CONSTRUCTION Filed Sept. 1.7, 1962 5 Sheets-Sheet 3 BY @11 M y W M ATTORNEYS United States Patent O 3,258,851 DRYER CGNSTRUCTION Raymond C. Vonderau, Beloit, Wis., assigner to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Sept. 17, 1962, Ser. No. 224,056 Claims. (Cl. 341-124) The present invention relates to improvements in dryer drums and more particularly to drums of the type for drying paper in a paper mill.

In drying a travelling web in a paper mill it is essential that the web be dried uniformly across its width and that the entire drying surface of the drum be maintained at a uniform temperature. Dryer drums are commonly heated by pressurized steam delivered to the interior of the drum, and condensate is removed from the inner surfaces of the hollow drum. To obtain uniform temperatures it is essential that the heat transfer rate be uniform throughout the length of the drum, and drums presently available are characterized by a drastic reduction in heat rate transfer towards the ends. The drums are constructed with a relatively thin shell for effective heat transfer and because of stress requirements and the need for attachment of the ends of the outer shell to the drum heads it is necessary to increase the thickness of the shell at the ends. This increased thickness reduces the heat transfer rate so that a lower temperature results on the drum surface towards the ends. At the point of `attachment of the ends of the outer shell to the drum heads the heat transfer rate increases again due to the influence of the drum heads. This results in a temperature pattern across the drying face of the drum which is constant for the major portion thereof, decreases towards the ends as the shell thickness increases and again increases in the area where the drum heads are attached to the outer shell.

It is also essential to efficient and uniform heat transfer to remove the condensate from the inner surface of the drum as uniformly and as rapidly as possible. Failure of the condensate removal system to eliminate condensate as rapidly as the steam is condensed will have an adverse effect on heat transfer and will increase the rotational driving load. On low speed machines the increase in load will be gradual, `and on high speed machines the condensate is held centrifugally around the entire surface of the dryer shell up to a certain weight, and when the weight exceeds its limit the condensate falls to the bottom of the shell and a sudden increase in load occurs imposing severe strains in the drive. It is therefore necessary to proper operation and to even drying to not only remove all of the condensate but to remove the condensate evenly across the length of the .inner surface of the shell of the drum.

While the features of the present Iinvention are well suited to effective use in a paper drying system, it will be appreciated that they may be employed in drying drums for other web drying uses or drums used for drying food products and similar requirements.

It is an object of the present invention to provide a dryer drum capable of sustaining loads and forces substantially equivalent to the loads imposed on conventional drums, but capable of substantially improved heat trans fer at the drum ends.

A further object of the invention is to provide a dryer drum which can be constructed of the same physical outside dimensions as drums heretofore available, but which affords a substantially increased effective drum width over which a uniform temperature'is maintained and a uniform heat transfer rate is obtained.

A still further object of the invention is to provide an improved dryer drum structure which has `axially extending ribs with channels therebetween at the ends of the drum and wherein an effective structure is provided for the removal of condensate collecting between the ribs.

A feature of the present invention is the provision of an improved cylindrical dryer drum having a cylindrical shell with heads attached at the ends to provide a chamber therein, wherein the shell is substantially of uniform thickness throughout its length for uniform heat transfer and has annular inner ribs throughout its length extending to the ends and at the ends is provided with uniformly circumferentially spaced radially linwardly projecting axially extending ribs projecting from the inner surface of the shell and having heat transfer areas therebetween with condensate removal suction orifices at the axial inner ends of the channels between the ribs.

Other objects, advantages and features will become more apparent with the teaching of the principles of the present `invention in connection with the disclosure of the preferred embodiment thereof in the specification, claims and drawings, in which:

FIGURE l is a vertical sectional View taken through a dryer drum of a type constructed in accordance with the principles of the present invention;

FIGURE 2 is an enlarged sectional fragmentary detailed view of one end of the drum;

FIGUR-E 3 is a fragmentary sectional view taken substantially along line III-III of FIGURE 2;

FIGURE 4 is a schematic View showing a section of the drum end according to this invention and a graph plotting heat transfer along the drum length; and

FIGURE 5 is a view similar to FIGURE 4 but showing heat transfer with constructions heretofore available.

On the drawings:

FIGURE 1 illustrates a dryer drum 10 as used in a paper machine which will yhave a web W of paper threaded over the smooth outer surface thereof -for removing water from the paper lby evaporation. The drum is constructed to maintain a substantially uniform heat along its length to the points E which mark the edges of the paper web which may be supported on the surfaces thereof. If the drum has no uniform heat and is at a lower temperature at the edges, the evaporation rate will be reduced at the ends resulting in a paper web with wet edges. These wet edges are detrimental to further paper operations such as reeling, winding and finishing, and the edges must therefore be discarded, or dried prior to such operations by means of auxiliary drying equipment. The drum may be of the type used for a paper dryer, `a Yankee dryer, a creping dryer or dryers for other purposes.

The dryer drum 10 includes a cylindrical outer shell 11 with inturned flanges 12 and 13a at the ends. These flanges attach to annular heads 13 and 14 such as by bolts 15. The heads are shown as bein-g mounted on a shell frame or core 16 which has bearing shafts 18 and 19 at its ends for bearings for rotatably supporting the drum. The shafts are hol-low and provide a passageway such as 20 for delivering heat transfer uid Isuch `as steam to the dryer drum. The steam enters the hollow core shaft 16 and is delivered to a chamber 22 within the shell through steam nozzles 21. Condensate is removed through a suction system having axial headers 22a in the drum, with outwardly projecting suction tubes 26 and 29, shown in FIGURES 2 and 3, but omitted from FIG- URE l for clarity.

FIGURES 2 and 3 show the construction at the ends of the shell 11; inasmuch as the ends may be identically made, only one end need be described in detail.

The shell is made of substantially uniform thickness for the uniform transfer of heat and has a plurality of annular rib-s which are not shown in detail in FIGURE 1.

Also omitted are radially extending drainage tubes. The

annular ribs 24 and tubes 26 and 29 are illustratedrin the detailed View of FIG-URE 2. The annular ribs 24 per-mit the use of a thinner shell while obtaining sufficient shell strength. Between the annular ribs are annular channels 25 and the effective heat transfer path distance for the steam is from the base of the channels 25 to the outer surface of the shell. By shell thickness T reference is then made to the thickness of the shell from the base of the channels 25 to the outer surface 23 of the shell. Substantially this same shell thickness or .a thickness only s-lightly larger is utilized at the 4shell ends just inside of the flanges 12 and 13a. For example a shell thickness T of 1%. inches may be used and an end shell thickness T inside the anges of 15/8 inches is then used. For strengthening the shell ends, radially inwardly extending ribs 27 are provided, as illustrated in FIGURES 2 and 3. These ribs have axial channels 2S between them, and as willbe seen the effective shell thickness T is used for substantially the same length of heat transfer path as the shell areas inwardly of the end.

For the removal of condensate between the ribs 27, condensate removal tubes 29 are positioned at the axial inner ends of the ribs at uniformly spa-ced circumferential positions around the Shell. The tubes lead into the headers 22a, extending radially therefrom along the length of the headers. The condensate thus will form and will be sucked through the orifice at the outer ends of the suction tubes 29, which draws the condensate from between the ribs. The inner ends of the ribs terminate to for-m a circumferential channel 30 at their axially inner ends, communicating with each of the condensate removal tubes 29. The channels 28v may slope slightly inwardly axially to the channel 30 for improved drainage. The ribs 27 may be considered as being elongate with their axes in the elongate direction and the axes extendin-g axially relative to the shell 11. The ribs or their axes may further be considered as being spaced in a circumferential direction with the ribs projecting radially inwardly on the inner surface of the shell 11 at the ends o-f the shell.

FIGURE 4 illustrates the heat transfer characteristic for the end of the shell 11. The lower .solid line of the graph represents the percentage heat transfer to the surface of the roll. The broken lines of the graph represent percentages of heat transmitted for different width webs and the broken line extends vertically at the web edge indicating free radiation of heat. The graph illustration has been made assuming 100% transfer through the shell portion inwardly of the ends at the location of the annular ribs 24. The heat transfer rate remains above 90% substantially as far as the location of the flange 12. As an example of structure, the graph of FIGURE 4 was plotted with the use of a l5 foot diameter drying drum with a shell thickness of 1% inches. The distance from point B to point C is 7 inches, and an additional inch can be effectively used for a drying width. Thus for the entire drum length, an increase o-f 16 inches ,has been achieved in effective shell length. In the side drum employed this amounted to an equivalent of a 71/2 increase in production (with the wet edges discarded).

'FIGURE 5 illu-strates heat transfer conditions with a dryer drum of conventional design wherein the ends of the shell were for-med of increased thickness for strength. Under the same operating conditions, heat transfer dropped from point B from 100% to 50% at point C and most of the area from B to C is unusable since inadequate drying of the web edges will occur. It has been found in practice that a drop of approximately l0-l5% in heat transfer rate through the shell is the maximum allowable for proper drying conditions. In the arrangement illustrated the reduction isl as much as 8 inches on either side. Extending the sheet trim beyond the 80% range of heat transfer will give wet sheet edges which are detrimental to reeling, winding and finishing operations and these edges m-ust be discarded or else dried by auxiliary -drying equipment.

The dryer shell end construction may .be used for both plain and grooved shells as well as for large and small diameter dryers.

The cost of machining the longitudinal ribs is not appreciable with respect to the total cost of manufacture, particularly on large Yankee dryers. The present structure will allow the use of rib dryers on existing installations without widening frames or bearing centers and yet increasing the effective shell width. The water removal arrangement is provided by the tubes 29, FIGURES 2 and 3, and it can be connected to the existing condensate evacuation system and the same principle and the same type of operation is employed as for evacuating condensate from the rest of the length of the shell of the dryer drum.

Thus it will be seen that I have provided an improved dryer drum construction which meets the objectives, advantages and features hereinabove set forth and which provides advantages over structures heretofore available.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not -limited to the specific forms disclosed, but covers vall modilications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim `as my invention:

1. A dryer drum comprising, a cylindrical shell having a smooth cylindrical outer heat transfer surface, end heads secured to the shell to provide a closed chamber within the shell, bearing means on the heads for rotatably supporting the drum, means for delivering heat transfer steam to said chamber, means for removing condensate from the inner surface of the shell, a plural-ity of elongate ribs with an axis in the elongate direction, said axis extending axially relative to the shell and the axes of said ribs being substantially uniformly spaced in a circumferential direction and said ribs projecting radially inwardly on the inner surface at the ends of the shell, and means for removing Acondensate collecting between said ribs.

2. A dryer drum comprising, -a cylindrical shell having a smooth cylindrical outer heat transfer surface, end heads secured to the shell lto provide a closed chamber within the shell, bearing means on the heads for rotatably supporting the drum, a plurality of uniformly spaced radially inwardly extending annular ribs on the inner surface of the shell, means for removing condensate from between said ribs, a plurality of elongate ribs each with an axis in the elongate direction, said axis extending axially relative to the shell and .the axis of said ribs being substantially uniformly spaced in a circumferential direction .and said ribs projecting radially inwardly on the inner surface at the ends of the shell, and condensate removing means positioned at the axially inner ends of the ribs removing condensate collecting between said ribs.

3. In a cylindrical dryer drum having a heat transferring outer Ishell and a chamber therein for lreceiving heat energy, a plurality of elongate ribs with an .axis in the elongate direction, said axis extending axially relative to the shell 'and the .axes of said ribs being circumferentially spaced with said ribs extending radially inwardly `at each end `of the shell with heat transfer areas therebetween.

4. In a cylindrical dryer drum having a heat transferring outer shell and a chamber therein lfor receiving heat ene-rgy, a plurality of elongate ribs wit-h an axis in the elongate direction, said axis extending axially relative to the shell and .the axes of said ribs being .circumferentially spaced with said ribs extending radially inwardly at each end 4of the shell with heat transfer areas therebetween, means for delivering steam to said chamber, and means for removing condensate from the chamber and from the areas between the ribs.

5. A dryer drum comprising, a cylindrical shell having a smooth cylindrical outer heat transfer surface, end heads secured to the shell to provide a closed chamber within the shell, bear-ing means on the heads for rotatably supporting the drum, means for delivering heat energy -to said chamber lfor conductive transfer through the shell, and a plurality of elongate ribs with an axis in the elongate direction, said laxis extending axially relative to the shell and the axes of said ribs being evenly spaced in a circumferential direction with said r-i-bs being -on each of the ends lof the inner surfaces of the shell ywith said shell being of substantially the same thickness lbetween said ribs as axially inwardly thereof.

6. A dryer drum comprising a cylindrical shell of uniyform thickness for uniform heat transfer therethrough, heads at the ends of the shell having means for rotatably supporting the dr-um, -rneans rfor delivering heat energy to the shell interior, annular ribs on the inner surface of the shell between the ends, and elongate `ribs with `an axis in the elongate direction, said axis extending axially relative to the shell and said .ribs being on the inner surface of the shell at the ends.

7. A dryer drum comprising a -cylindrical shell of uniform thickness `for yuniform heat transfer therethrough, heads at the ends of lthe shell having means for rotatably supporting the drum, means |for ydeliverin-g steam to the interior of the shell, annular ribs `on the inner surface of the shell between the ends, elongate ribs with an .axis in the elongate direction, said axis extending axially relative to the shell and said ribs being on the inner surface of the shell at the ends, first -means Iremoving condensate from between each of the annular ribs, and second means removing condensate `from between the elongate ribs.

8. In a cylindrical dryer drum having a heat transferring outer shell and a chamber therein for receiving heat energy, a plurality of elongate ribs with an axis in the elongate direction, said ribs extending axially relative to the shell and the axes of said ribs being -circurnferentially spaced, said r-ibs extending radially inwardly at each end of the shell 'with heat transfer areas therebetween, means for delivering steam to said chamber, and means at the axial inner ends of the ribs adjacent lthe inner surface of the shell for removing condensate flowing axially from between the ribs.

9. In a lcylindrical dryer `drum having a lheat transferring Aouter shell and a chamber ltherein for receiving heat energy, a plurality of elongate ribs With an -axs in the elongate direction, said axis extending axially relative to the shell and the axes of said ribs ybeing spaced circumferentially with said ribs extending radially inwardly at each end of the -shell with heat `transfer areas therebetween, means for delivering steam to said chamber, and a plurality of equal-ly circumferentially spaced suction members at the axial linner ends of the channels formed by said ribs for withdrawing condensate from the inner surface of the drum.

10. A dryer drum comprising a cylindrical shell having a smooth cylindrical outer heat transfer surface, inwardly turned rflanges at the ends of the shell, annular end heads secured to said flanges, a core extending through said heads and secured thereto provided with shafts for rotatably supporting the drum, a steam supply passage through the shaft at one end of the drum, steam distribution nozzles connected to the passage for directing steam into the interior of the shell, condensate collecting means within the inner `surface of the shell for removing condensate, a plurality of inwardly projecting axially extending circumferentially spaced ribs having channels therebetween joining the end flan-ges of the shell and positioned at each end, said r-ibs extending axially inwardly a relatively short distance tfrom the ends of the shell, said shell being of uniform thickness throughout its length and at said channels, and a plurality of c-ircumferentially -spaced condensate removing tubes having openings at the axial inner ends `of the channels formed by said ribs for removing condensate owing axially inwardly in said channels.

References Cited by the Examiner UNITED STATES PATENTS 2,328,321 8/1943 Berry 34-124 X 2,486,719 ll/l949 Messinger 34-124 2,521,371 9/1950 Hornbostel et al. 34-125 2,987,305 6/ 1961 Calhoun 263-6 FOREIGN PATENTS 618,348 4/1961 Canada. 497,034 5 1930 Germany.

WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFP, Examiner.

J. SOFER, B. L. ADAMS, Assistant Examiners. 

10. A DRYER DRUM COMPRISING A CYLINDRICAL SHELL HAVING A SMOOTH CYLINDRICAL OUTER HEAT TRANSFER SURFACE, INWARDLY TURNED FLANGES AT THE ENDS OF THE SHELL, ANNULAR END HEADS SECURED TO SAID FLANGES, A CORE EXTENDING THROUGH SAID HEADS AND SECURED THERETO PROVIDED WITH SHAFTS FOR ROTATABLY SUPPORTING THE DRUM, A STEAM SUPPLY PASSAGE THROUGH THE SHAFT AT ONE END OF THE DRUM, STEAM DISTRIBUTION NOZZLES CONNECTED TO THE PASSAGE FOR DIRECTING STEAM INTO THE INTERIOR OF THE SHELL, CONDENSATE COLLECTING MEANS WITHIN THE INNER SURFACE OF THE SHELL FOR REMOVING CONDENSATE, A PLURALITY OF INWARDLY PROJECTING AXIALLY EXTENDING CIRCUMFERENTIALLY SPACED RIBS HAVING CHANNELS THEREBETWEEN JOINING THE END FLANGES OF TEH SHELL AND POSITIONED AT EACH END, SAID RIBS EXTENDING AXIALLY INWARDLY A RELATIVELY SHORT DISTANCE FROM THE ENDS OF THE SHELL, SAID SHELL BEING OF UNIFORM THICKNESS THROUGHOUT ITS LENGTH AND AT SAID CHANNELS, AND A PLURALITY OF CIRCUMFERENTIALLY SPACED CONDENSATE REMOVING TUBES HAVING OPENINGS AT THE AXIAL INNER ENDS OF THE CHANNELS FORMED BY SAID RIBS FOR REMOVING CONDENSATE FLOWING AXIALLY INWARDLY IN SAID CHANNELS. 